Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes

Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes Biotreatment of industrial effluents CHAPTER 10 – degradation of dyes

CHAPTER 10 Degradation of Dyes Dyestuffs can be classified according to their origin, chemical and/or physical properties, or characteristics related to the application process Another categorization is based on the applications sector (e.g., inks, disperse dyes, pigments, or vat dyes) A systematic classification of dyes according to chemical structure is the color index, namely, nitroso, nitro, monoazo, disazo, trisazo, polyazo, azoic, stilbene, carotenoid, diphenylmethane, triarylmethane, xanthene, acridine, quinoline, methine, thiazole, indamine/indophenol, azine, oxazine, thiazine, sulfur, lactone, aminoketone, hydroxyketone, anthraquinone, indigoid, phthalocyanine, natural, oxidation base, and inorganic Synthetic dyes are also classified according to their most predominant chemical structures, namely, polyene and polymethine, diarylmethine, triarylmethine, nitro and nitroso, anthraquinone, and diazo (Fig 10-1 ) Approximately 10,000 different dyes and pigments are manufactured worldwide with a total annual market of more than x 105 tonnes per year There are several structural varieties of dyes, such as acidic, reactive, basic, disperse, azo, diazo, anthraquinone-based, and metal-complex dyes They all absorb light in the visible region Untreated dye effluent is highly colored and hence reduces sunlight penetration, preventing photosynthesis Many dyes are toxic to fish and mammalian life, inhibit growth of microorganisms, and affect flora and fauna They are also carcinogenic in nature and hence can cause intestinal cancer and cerebral abnormalities in fetuses The physical and chemical methods for the treatment of dye-containing effluent includes physicochemical flocculation combined with flotation, electroflotation, flocculation with Fe(II)/Ca(OH)9., membrane filtration, electrokinetic coagulation, electrochemical destruction, ion-exchange, irradiation, photochemical precipitation, oxidation, ozonation, adsorption with activated carbon, and the Katox treatment method, which involves the use of activated carbon and air mixtures The chemical color removal process leads to 60 to 70% reduction in the color, while the decrease in biological oxygen demand (BOD)is only about 30 to 40% (Cooper, 1993; Nowak, 1992; Zamora et al., 1999) 111 112 Biotreatment of Industrial Effluents H3C \ CH3 H3C/N N~CH3 Diarylmethinedye H3C jN H3C ~ H3C /N'~'CH3 Triarylmethinedye HC Polyeneandpolymethine NH ~ O3H Nitroandnitrosodyes O NH2 SO3H Anthraquinonicdye O HN., NzN _N~N ~ NH-~~ \\ /~~O~H HO3S Diazodyes FIGURE 10-1 Structure of dyes based on predominant groups Degradation of Dyes 113 Textile Dyes Textile industries consume two thirds of the dyes manufactured The requirement for reactive dyes is high since cotton fabric with brilliant colors has a high demand The reactive dyes bind to the cotton fibers by addition or substitution mechanisms under alkaline conditions and high temperature Also, a significant fraction of the dye is hydrolyzed and released Colored wastewater is a consequence of batch processes both in the dyemanufacturing and the dye-consuming industries Two percent of dyes that are produced are discharged directly in the effluent, and a further 10% is lost during the textile coloration process Generally the wastewater contains dye concentrations around 10 to 200 mg/L, as well as other organic and inorganic chemicals used in the dyeing process The wastewater discharged from a dyeing process in the textile industry is highly colored and has low BOD and high chemical oxygen demand (COD)(because of the presence of grease, dirt, and/or sizing agents, as well as nutrients from dye bath additives) Alkali or acids from the bleaching, desizing, scouring, and mercerizing steps also end up in the effluent, resulting in extreme pH and high salt content (Chapter 11 deals with textile effluent) Conventional biological processes have also been resorted to for the treatment of textile wastewater This includes adsorption of dyestuff on activated sludge (Hu and Ko, 1992), decolorization of reactive azo dyes by transformation using Pseudomanas luteola (Hu, 1994), and biosorption of cationic dyes by dead macrofungus Fomitopsis carnea (Mittal and Gupta, 1996) Activated sludge has also been used as biomass in the adsorption of dyestuff, achieving about 90% of BOD, 40 to 50% of COD reduction, and 10 to 30% of color removal (Pagga and Taeger, 1994; Hitz et al., 1978) Aerobic biological treatment alone generally cannot effectively decolorize wastewaters containing water-soluble dyes; hence a chemical treatment is a necessary primary stage Effluent collected from a textile mill was chemically treated with sodium bisulfite and sodium borohydride as the catalyst and reduction agent, respectively, followed by aerobic biological oxidation leading to an 80% reduction in color, 98% reduction in BOD, 80% reduction in COD, and 95% reduction in TSS (Ghoreishi and Haghighi, 2003 ) Reactive azo dyes, which are used for dyeing cellulose, produce the colored wastewater (Fig 10-2) These dyes make up ~ 30% of the total dye market Because of their stability and xenobiotic nature, reactive azo dyes are not totally degraded by conventional wastewater treatment processes that involve light, chemicals, or activated sludge Azo dyes are not readily metabolized under aerobic conditions Under anaerobic conditions, many bacteria reduce the electrophilic azo bond in the dye molecule to colorless amines Although these amines are resistant to further anaerobic mineralization, they are good substrates for aerobic degradation through a hydroxylation pathway involving a ring-opening mechanism Hence a combined anaerobic 114 Biotreatment of Industrial Effluents Xenobiotic hydrazone and azo bonds are part of the chromophore ) o oII " o Xenobiotic aromatic sulfonic acid groups make the dye highly soluble in water FIGURE 10-2 A typical reactive dye structure with its chromophore, containing azo/keto-hydrazone groups, the reactive centers and its solubilizing components (Remazol Black Bm a reactive azo dye) treatment followed by an aerobic one could be very effective Microbial species, including bacteria, fungi, and algae, can remove the color of azo dye via biotransformation, biodegradation, or mineralization Decolorization of azo dyes by bacteria is carried out by azoreductase-catalyzed reduction or by cleavage of azo bonds under anaerobic environment Pearce et al (2003) have listed various literature examples dealing with mixed cultures and single bacterial strains that have been found to degrade these dyes effectively A few examples of mixed culture include Bacillus cereus, Sphaerotilus natans, Arthrobacter sp., or activated sludge under anoxic conditions for reduction of azo dyes; Alcaligenes faecalis and Commomonas acidovorans for decolorization of reactive dyes, diazo dyes, azo dyes, disperse dyes, and phthalocyanine dyes under anaerobic conditions; Alcaligenes faecalis and Commomonas acidovorans have been used for the degradation of Remazol Black B In addition, aerobic bacterial sludge and aerobic activated sludge have been used for degrading various azo, diazo, and reactive dyes A few examples of single bacterial strains include Proteus vulgaris under anaerobic conditions for treating azo food dyes; Pseudomonas pseudomallei for treating acid, direct, and basic dyes; immobilized Pseudomonas sp for dyes having anthraquinone and metal-complex structures; Streptococcus faeclis for treating Red 2Gazo dye; Pseudomonas luteola for treating reactive azo dyes, direct azo dyes, and leather dyes, Paenibacillus azoreducens sp nov for treating Remazol Black B, and Shewanella putrefaciens for treating Remazol Black B and anthraquinone dyes Two mechanisms for the decoloration of azo dyes under anaerobic conditions in bacterial systems have been proposed (Keck et al., 1997; Pearce et al., 2003) The first one consists of direct electron transfer to azo dyes as Degradation of Dyes Colored solution containing dye X 115 Colorless solution containing amines X I, Chromophore N Redox mediator ox Redox mediator red H2N Azoreductase NADH NAD+ X Carbon complexes Oxidation products Dehydrogenase (enzyme liberating e-) FIGURE 10-3 A proposed redox reaction for the degradation of azo dyes with whole bacterial cells terminal electron acceptors via enzymes during bacterial catabolism, connected to ATP-generation (energy conservation) The second one involves a free reduction of azo dyes by the end products of bacterial catabolism, not linked to ATP generation (e.g., reduction of the azo bond by reduced inorganic compounds, such as Fe z+ or H2S, that are formed as the end product of certain anaerobic bacterial metabolic reactions) Figure 10-3 shows a possible pathway for the degradation of azo dyes under anaerobic conditions with whole bacterial cells During anaerobic degradation, a reduction of the azo bond in the dye molecule is observed Then, aerobic conditions are required for the complete mineralization of the reactive azo dye molecule The aromatic compounds produced by the initial reduction are degraded via hydroxylation and ring opening in the presence of oxygen So for effective wastewater treatment, a two-stage process is necessary in which oxygen is introduced after the initial anaerobic reduction of the azo bond has taken place The optimum pH for color removal is around pH to 7.5 The rate of color 116 Biotreatment of Industrial Effluents removal tends to decrease rapidly under strongly acid or strongly alkaline conditions The optimum cell culture growth temperature is between 35 and 45~ Operating Conditions The efficiency of color removal depends on several factors, which include level of aeration, temperature, pH, and redox potential The composition of textile wastewater is varied and can include in addition to the color, organics, nutrients, salts, sulfur compounds, and toxicants The concentration of dye in the solution affects the rate of biodegradation; possible reasons include toxicity of the dye, toxicity of the metabolites formed during the degradation of the dye molecule, and ability of the enzyme to recognize the dye efficiently at very low concentrations It has been found that during the decolorization of triphenylmethane dyes and textile dyestuff, effluent by Kurthia sp was facile at low dye concentrations But when the dye concentration was increased (~30 mM), the rate of color removal was reduced (Sani et al., 1999) If the dye reduction mechanism is nonenzymatic, then the reduction rate will be independent of the dye concentration This type of behavior has been observed during the reduction of azo food dyes in cultures of Proteus vulgaris (Dubin and Wright, 1975) It has been observed that simple structures and low molecular weight dyes degrade faster than highly substituted, high molecular weight dyes If the dye reduction happens inside the cell, then the first step is diffusion of the molecule through the cell membrane The presence of a sulfonate group could hinder this transfer rate, and the rate decrease could be proportional to the number of sulfonate groups Of course, cultures could be adapted to produce azoreductase enzymes that have very high specificity toward particular dye structures In addition, hydrogen bonding and electronegativity could affect the reduction rate Redox potential is a measure of the ease with which a molecule will accept electrons, which means that the more positive the redox potential, the more readily a molecule is reduced The rate-controlling step in the dye reduction reaction involves a redox equilibrium between the dye and the extracellular reducing agent (see Fig 10-3) The color removal process thus depends on the redox potential of the electron donors and acceptors Different electron donors such as glucose, acetate, formate, etc., have different effects on the degradation reaction Enzymic reduction of azo groups is normally inhibited by dissolved oxygen; hence it is necessary that bacterial decolorization take place under nearly anaerobic conditions Cell immobilization through entrapment with natural or synthetic materials is an ideal technique, which can create a local anaerobic environment favorable to oxygen-sensitive decolorization Cell immobilization also enhances the stability, mechanical strength, and reusability of the biocatalyst Degradation of Dyes 117 Free and supported Pseudomonas luteola was able to reduce azo groups of C.I Reactive Red 22 enzymatically (Chang et al., 2001 ) Immobilized cells exhibited lower activity because of mass transfer effects and were also less sensitive to dissolved oxygen levels and pH as compared with free suspended cells The decolorization activity in all the cases increased as the temperature increased from 20 to 45~ (Mechsner and Wuhrmann, 1982) Laccase immobilized on various supports decolorized textile reactive dyes (Dias et al., 2004) The initial decolorization observed is due to the adsorption of the dye to the support, and the later decolorization is due to the enzymatic reaction When the system is preirradiated, the reaction time is faster, probably because the small molecular fragments that are formed during the irradiation process are more compatible with the subsequent enzymatic process (Zamora et al., 2003) Use of enzyme for decolorization has several advantages over the use of fungi or bacteria They include the absence of a lag phase, generation of a low amount of sludge, ease of controlling the process, and ability to operate the reactor at low or high contaminant concentration Fungi capable of decolorization include Aspergillus sojae B-10, Myrothecum verrucaria, Myrothecum sp., Neurospora crassa, and Candida sp (Banat et al., 1996) A fungal strain ATCC 74414 isolated from a plant anise, Pimpinella anisum, aerobically decolorized two polymeric dyes, namely, Poly R-478 and Poly S-119 in liquid media; the process involved two steps: adsorption of the dye compound by fungal mycelia followed by biodegradation through microbial metabolism (Zheng et al., 1999) Bacterial cultures capable of dye decolorization include Aeromonas hydrophila var 24B, Pseudomonas luteola, P cepacia, and Streptomycetes BWI30 (Banat et al., 1996) Algal cultures Chlorella and Oscillatoria were able to degrade dyes to aromatic amines and subsequently to simpler compounds Geotrichum candidum Dec exhibits aerobic dye-decolorizing ability for 21 kinds of azo and anthraquinone dyes It requires an external carbon source Reactors White rot fungi have been used for the decomposition of several recalcitrant dyes in different reactor configurations, including fixed-film bioreactors (for the decolorization of dispersed dyes), packed bed reactors, rotating biological contactors, and pulsed flow reactors Generally the operations were carried out either in batch or semibatch mode, although a few studies have reported using continuous mode When carried out in rotating biological contactors, the degradation efficiency for decolorization of dispersed dyes was found to depend on the biofilm thickness, rotational speed, and carbon source concentration Pulsed flow systems introduce oxygen in pulses The white-rot fungus, Pycnoporus cinnabarinus, was found to decolorize high concentrations of dyes in a packed-bed reactor 118 Biotreatment of Industrial Effluents Selvam et al (2003) have carried out treatment of dye industry effluent in batch and continuous modes using mycelia of Thelephora sp Interestingly, they observed degradation rates that were higher in the batch mode (61% color removed in days) as against continuous mode, where there was 50% color removal Biodegradation of a simulated cotton textile effluent containing azo and diazo dyes was attempted in an anaerobic-aerobic sequencing batch reactor (SBR) A 24-h cycle with 10 h aeration time and 14 h of anaerobic time achieved 90% color removal Fu et al (2001 ) achieved 66 % biodegradation of reactive dye in a similar reactor When the same reaction was carried out in a two-reactor system, where one was anaerobic and the other aerobic, the degradation efficiency was 88% Acid red 151 was aerobically biodegraded with an average efficiency of 88% in a sequencing batch biofilter using porous volcanic rock as packing (Buitron et al., 2004) The majority of the dye was transformed to CO2 It was also found that 14 to 16 % of the biotransformation was due to the anaerobic environments inside the porous support material Anaerobic degradation of black, red, and blue reactive dyes showed different results in a two-stage upward aerobic sludge blanket (UASB) system consisting of an acidification tank and in a reactor with and without the addition of an external carbon source such as tapioca starch (Chinwetkitvanich et al., 2000) Tapioca had no effect in the case of black dye, since the decolorization efficiency remained at ~ 70% Degradation efficiency increased from 36 to 56 % in the case of red dye and from 48 to 56% in the case of blue dye on the addition of tapioca In these studies there was no correlation between the color removed and the amount of methane formed, indicating that methane-forming bacteria were not the only anaerobic microorganisms responsible for color removal But Carliell et al (1996) and Razo-Flores et al (1997) suggested that during the methane production step of anaerobic decolorization, when the methanogenic bacteria used the azo bonds in the chromophores of the dye as electron acceptors, the azo bond was broken, resulting in the decolorization Anaerobic degradation on the order of 30 to 35 % in COD was observed for six textile print dyes of various classes (azo, anthraquinone, cyanine, etc.) in an up-flow filter with milk whey as cosubstrate It is thought that methanogenesis is inhibited by chemicals in the thickener, including surfactants and chelating agents, and by the high ammonia concentration in the filter due to hydrolysis of the urea present in the thickener Eighty percent decolorization was observed in 24 hours and complete degradation in days when textile dyes (Remazole Navy Blue and Red, Remazol Blue, Turquoise Blue, Black, Golden Yellow) were treated in a submerged anaerobic biofilm reactor with Alcaligenes faecalis and Comomonas acidovorans strains (Banat, 1996) A fixed-bed reactor coupled with a pneumatic pulsation system has been found to increase the mass transfer rate and to enhance productivity for yeast and fungi systems A similar design was found to be very effective Degradation of Dyes 119 for treating anthraquinone type (Poly R-478), azo type (Orange II), and phtalocyanine type (Reactive Blue 98) dyes The decolorization efficiencies were on the order of 98 % for several months at a dye loading of 0.2 g dye/m 3/day Ninety-five percent continuous decolorization of Orange II dye using manganese peroxidase (MnP) in a continuous stirred tank reactor coupled with an external membrane unit as a filter was observed by L6pez et al (2002) The MnP, dye, and hydrogen peroxide were added continuously White Rot Fungi White rot fungi are a heterogeneous group of organisms that have the capability of degrading lignin, several wood components, and many recalcitrant compounds The enzymes are extracellular (limitations caused by substrate diffusion into the cell, generally encountered in bacteria, are not observed here), nonspecific (they can degrade a wide variety of recalcitrant compounds and even complex mixtures of pollutants), can tolerate a high concentration of pollutants, and are nonstereoselective They also not require any preconditioning since enzyme secretion depends on nutrient limitation, either nitrogen or carbon, and not on the presence of pollutant Manganese peroxidases, lignin peroxidases, and laccases are the three lignin-modifying enzymes present that help to degrade lignin and various xenobiotic compounds including dyes The main disadvantages are the low pH requirement for optimum activity of the enzymes, the complexity of the biodegradation mechanism of the ligninolytic system, and a requirement for some chemicals unlikely to be present in the wastewater Several white rot fungi studied for color removal include Bjerkandera adusta for degrading reactive Orange, Violet, Black and Blue; Irpex lacteus for degrading Methyl Red, Congo Red, and Naphtol Blue; Phanerochaete chrysosporium for degrading Remazol Turquoise Blue, azo dyes, Azure Blue, and Cresol Red; Phlebia radiata for degrading orange II and reactive blue; Pleurotus ostreatus for degrading Remazol Brilliant Blue and Poly R-478; and Pycnoporus sanguineus for degrading Orange G, Amaranth, Bromophenol Blue, and Malachite Green and several more Phanerochaete chrysosporium has been found to degrade sulfonated azo dyes, heterocyclic, polymeric, anthraquinone, triphenylmethane, and azo dyes The mechanism of color removal involves a lignin peroxidase and Mn-dependent peroxidase or laccase enzymes Decolorization studies carried out by Selvam et al (2003) of azo dyes Orange G, Congo Red, and Amido Black by a white rot fungus Thelephora sp showed that the fungus was able to completely degrade (98%) Amido Black 10B in 24 h and Congo Red (> 97%) in h Only 33.3% of Orange G degraded in days An activated sludge reactor containing white-rot fungus Coriolus versicolor could degrade 82% of a textile dye Everzol Turquoise Blue G (Kapdan and Kargi, 2002) Yang and Yu (1996) achieved 80% degradation 120 B i o t r e a t m e n t of I n d u s t r i a l Effluents of a dispersed dye in a continuous fixed-film bioreactor Zhang et al (1999) used a packed-bed reactor for the treatment of an azo dye, Orange II, and reached efficiencies on the order of 90% The main problem in using white rot fungi for continuous effluent treatment is that they form a thick mycelial mat that can disrupt the reactor operation Conclusions Several chemical and physical methods are available for the removal of color from the textile dye effluent Decolorization by aerobic bacteria occurs mainly by adsorption of dyestuff on the cell surface rather than by biodegradation; therefore, low color removal efficiencies have been observed However, anaerobic bacteria provide better COD and total organic carbon (TOC) removal than anaerobic bacteria The combination of anaerobic bacteria followed by aerobic bacteria is found to be very effective Addition of adsorbent also provides several advantages including adsorption of toxic compounds, which reduces toxic effects on the microorganisms, and better sludge settling characteristics The extracellular ligninolytic enzyme systems of the white-rot fungi Phanerchaete chrysosporium and Coriolus versicolor can degrade a wide variety of recalcitrant compounds, including xenobiotics, lignin, and dyestuffs Several different reactors have been tried to achieve color removal, and a large number of bacteria and fungi have been identified as effective in this regard References Banat, I M., P Nigam, D Singh, and R Marchant 1996 Microbial decolorization of textiledye-containing effluents: a review Bioresour Technol 58:217-227 Buitron, G., M Quezada, and G Moreno 2004 Aerobic degradation of the azo dye acid red 151 in a sequencing batch biofilter Bioresour Technol 92:143-149 Carliell, C M., S J Barclay, and C A Buckley 1996 Treatment of exhausted reactive dyebath effluent using anaerobic digestion: laboratory and full-scale trials Water SA 22(3):225-233 Chang, J S., C Chou, and S.-Y Chen 2001 Decolorization of azo dyes with immobilized Pseudomonas luteola Process Biochem 36:757-763 Chinwetkitvanich, S., M Tuntoolvest, and T Panswad 2000 Aerobic decolorization of reactive dyebath effluents by a two-stage UASB system with tapioca as a co-substrate Water Res 34(8):2223-2232 Cooper, P 1993 Removing color from dye house wastewaters m a critical review of technology available J Soc Dyers Colorists 109:97-100 Dias, A A., R M Bezerra, and A N Pereira 2004 Activity and elution profile of Laccase during biological decolorization and dephenolization of olive mill waste water Bioresour Technol 92(1):7-13 Dubin, P., and K L Wright 1975 Reduction of azo food dyes in cultures of Proteus vulgaris Xenobiotica 5(9):563-71 Fu, L., and Q L Y Qian 2001 Treatment of dyeing waste water in two SBR systems Process Biochem 36(11):1111-1118 Ghoreishi, S M., and R Haghighi 2003 Chemical catalytic reaction and biological oxidation for treatment of non-biodegradable textile effluent Chem Eng J 95:163-169 Degradation of Dyes 121 Hitz, H R., W Huber, and R H Reed 1978 The adsorption of dyes on activated sludge J Soc Dyers Colorists 94:71-76 Hu, T L 1994 Decolorization of reactive azo dyes by transformation of Pseudomanas luteola Bioresour Technol 49:47-51 Hu, T L., and W L Ko 1992 Adsorption of reactive dyes by biomass, in: Proceedings of the 17th Conference on Wastewater Treatment Technology, China, pp 105-116 Kapdan, K I., and F Kargi 2002 Simultaneous biodegradation and adsorption of textile dyestuff in an activated sludge unit Process Biochem 37:973-981 Keck A., J Klein, M Kudlich, A Stolz, H.-J Knackmuss, and R Mattes 1997 Reduction of azo dyes by redox mediators originating in the naphthalenesulfonic acid degradation pathway of Sphingomonas sp strain BN6 Appl Environ Microbiol 63(9):3684-90 L6pez, C., I Mielgo, M T Moreira, G Feijoo, and J M Lema 2002 Enzymatic membrane reactors for biodegradation of recalcitrant compounds Application to dye decolourisation J Biotech 99:249-257 Mechsner K., and K Wuhrmann 1982 Cell permeability as a rate limiting factor in the microbial reduction of sulfonated azo dyes Europ J Appl Microbiol Biotechnol 15:123-126 Mittal, A K., and S K Gupta 1996 Biosorption of cationic dyes by dead macro-fungus Fomitopsis carnea: batch studies Water Sci Technol 34:81-87 Nowak, K M 1992 Color removal by reverse osmosis J Membr Sci 68:307-315 Pagga, U., and K Taeger 1994 Development of a method for adsorption of dyestuff on activated sludge Water Res 28:1051-1057 Pearce, C I., J R Lloyd, and J T Guthrie 2003 The removal of colour from textile wastewater using whole bacterial cells: a review Dyes and Pigments 58:179-196 Razo-Flores, E., M Luijten, B Donlon, G Lettinga, and J Field 1997 Biodegradation of selected azo dyes under methanogenic conditions Water Sci Technol 36(67):65-72 Sani, R K., and U C Banerjee 1999 Decolorization of triphenylmethane dyes and textile and dye-stuff effluent by Kurthia sp Enzyme Microbial Technol 24:433-437 Selvam, K., K Swaminathan, and K.-S Chae 2003 Decolourization of azo dyes and a dye industry effluent by a white rot fungus Thelephora sp Bioresour Technol 88:115-119 Yang, F C., and J T Yu 1996 Development of a bioreactor system using an immobilised white-rot fungus for decolorization Part II: continuous decolorization tests Bioprocess Eng 16:9-11 Zamora, P P., A Kunz, S Gomes de Moraes, R Pelegrini, P de Campos Molelro, J Reyes, and N Duran 1999 Degradation of reactive dyes in a comparative study of ozonation enzymatic and photochemical processes Chemosphere 38(4):835-852 Zhang, F., J S Knapp, and K.N Tapley 1999 Development of bioreactor systems for decolourisation of Orange II using white-rot fungus Enzyme Microbiol Technol 24:48-53 Zheng, Z., R E Levin, J L Pinkham, and K Shetty 1999 Decolorization of polymeric dyes by a novel Penicillium isolate Process Biochem 34:31-3 Bibliography Banas, J., E Plaza, W Styka, and J Trela 1999 SBR technology for advanced combined municipal and tannery wastewater treatment with high receiving water standards Water Sci Technol 40(4-5):451-458 Bernet, N., N Delgenes, J C Akunna, J P Delgenes, and R Molleta 2000 Combined anaerobic-aerobic SBR for the treatment of piggery wastewater Water Res 34(2):611-619 Helmreich, B., D Schreff, and P A Wilderer 2000 Full-scale experiments with small sequencing batch reactor plants in Bavaria Water Sci Technol 41(1):89-96 Kim, S J., K Ishikawa, M Hirai, and M Shoda 1995 Characteristics of a newly isolated fungus, Geotrichum candidum Dec 1, which decolorizes various dyes I Ferment Bioeng 79:601-607 122 Biotreatment of Industrial Effluents Lourenc, N D., J M Novais, and H M Pinheiro 2001 Effect of some operational parameters on textile dye biodegradation in a sequential batch reactor J Biotechnol 89:163-174 Malpei, F., V Andreoni, D Daffonchio, and A Rozzi 1999 Anaerobic digestion of print pastes: A preliminary screening of inhibition of dyes and biodegradability of thickeners Bioresour Technol 63:49-56 Mielgo, I., M T Moreira, G Feijoo, and J M Lema 2001 A packed-bed fungal bioreactor for the continuous decolourisation of azo-dyes (Orange II) J Biotechnol 89:99-106 Shaul, G M., T J Holdsworth, C R Dempsey, and K A Dostall 1991 Fate of water soluble azo dyes in the activated sludge process Chemosphere 22:107-119 Zamora, P P., C M Pereira, E R L Tiburtius, S G Moraes, M A Rosa, R C Minussi, and N Dur~in 2003 Decolorization of reactive dyes by immobilized laccase Appl Catal., B: Environ 42:131-144  ... NH-~~ \ /~~O~H HO3S Diazodyes FIGURE 10- 1 Structure of dyes based on predominant groups Degradation of Dyes 113 Textile Dyes Textile industries consume two thirds of the dyes manufactured The requirement... of reactive dyes, diazo dyes, azo dyes, disperse dyes, and phthalocyanine dyes under anaerobic conditions; Alcaligenes faecalis and Commomonas acidovorans have been used for the degradation of. .. of dyes in a packed-bed reactor 118 Biotreatment of Industrial Effluents Selvam et al (2003) have carried out treatment of dye industry effluent in batch and continuous modes using mycelia of